Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$37.99	9.618%	$41.6439	$41.64	$41.65	$41.60
Purchase #2	$81.29	12.457%	$91.4163	$91.42	$91.40	$91.40
Purchase #3	$164.62	5.805%	$174.1762	$174.18	$174.20	$174.20
Purchase #4	$244.82	4.817%	$256.613	$256.61	$256.60	$256.60
Purchase #5	$91.56	9.811%	$100.543	$100.54	$100.55	$100.50
Purchase #6	$179.25	5.260%	$188.6786	$188.68	$188.70	$188.70
Purchase #7	$49.37	9.387%	$54.0044	$54.00	$54.00	$54.00
7 purchase totals =	$848.90		$907.0754	$907.07	$907.10	$907.00